In a treating process for various types of workpieces such as a semiconductor wafer, liquid crystal glass, and so forth, an ionizer is used for discharging the workpiece, which is electrostatically charged. The ionizer is constructed, as described in, for example, Japanese Unexamined Patent Application Publication No. 2005-108829, such that a positive electrode needle and a negative electrode needle are disposed in parallel with each other in an electrode-attaching opening at a lower surface of a housing, and that positive and negative ions are alternately generated by generating a corona discharge at both the electrode needles by means of alternately applying a positive pulsing high voltage and a negative pulsing high voltage to these electrode needles.
Further, an air-blowing outlet is opened at a position between the positive and negative electrode needles, and air is blown out from the air-blowing outlet. Thereby, the ion generated by the electrode needles is brought in, and thereby the air is ionized and blown to the workpiece.
In this kind of ionizer, the positive and negative electrode needles tend to foul by adhesion of dust in the air, and when the fouling operation proceeds, a generating amount of the ion is being reduced because of the generation of the corona discharge gradually becomes difficult. Therefore, there is a possibility that the generation of the ions is finally stopped. Therefore, this requires frequent maintenance such as a cleaning operation, an exchanging operation, and so forth for the foul electrode needle, and during the time when the maintenance is performed, operations of the ionizer and related facilities have to be stopped. Consequently, there has been a problem such as that an operating efficiency tends to be lowered while taking trouble and wasting time.